The Alaska Wildlife Notebook Series (click on link) is a great informational resource provided by the Alaska Dept. of Fish and Game. Containing biological and species descriptions for well over a hundred Alaskan mammal, bird, & fish species; the Notebook Series gives you a great overview of our wild residents.

Here is  a small excerpt from Arctic Grayling

Life history:Grayling have evolved many strategies to meet the needs of life in what are often harsh and uncertain environments. Grayling can be highly migratory, using different streams for spawning, juvenile rearing, summer feeding, and overwintering. Or, in other areas, they can complete their entire life without leaving a short section of stream or lake. Winter generally finds grayling in lakes or the lower reaches and deeper pools of medium-sized rivers such as the Chena and Gulkana, or in large glacial rivers like the Tanana, Susitna, and Yukon. Their tolerance of low dissolved oxygen levels allows grayling to survive the long winters in areas where many other salmonids would die. With the coming of spring, grayling begin an upstream migration to spawning grounds. Like salmon, grayling faithfully return every year to the same spawning and feeding areas. Grayling spawn for the first time at an age of 4 or 5 years and a length of about 11 to 12 inches.